806 MR D. FERGUSON ON 



Harbour. When the centre of the fold was depressed to its full extent the rocks 

 snapped along its axis, and the sinking of the north side of the fold produced the 

 crumpling which can be noted in PI. LXXXV, fig. 2. The rocks which divide 

 the glacier of Leith Harbour into two parts are on the line of weakness and 

 fracture. Leith Harbour is simply a drowned land valley due to a general sinking 

 of the island. 



The rocks surrounding Leith Harbour belong to the middle division of the 

 Cumberland Bay Series. At the south-east corner, turning into Nansen Harbour, the 

 lower division comes in directly under the middle division and is represented by 

 fairly thick bodies of black cherty shales, grey arenaceous rocks, greywackes, and 

 tuffs. These rocks are faulted in places and tilted at slight angles. Further up 

 Nansen Harbour they dip more steeply under sea-level, and on the south side of the 

 harbour only the rocks of the middle division are seen. 



Husvik Harbour and the greater part of the southern shore of Stromness Bay are 

 formed of rocks of the middle division of the Cumberland Bay Series. Tonsberg 

 Point and the western half of Mutton Island belong entirely to the lower 

 division. The eastern half of Mutton Island has some blue-purple shales along the 

 line of rupture. These may be a fragment of the upper division and similar to the 

 shales of Bird Island. 



Fossil Impressions in the Lower Division at Leith Harbour. — The dark shales 

 and the fine arenaceous shales forming a rocky promontory where Leith Harbour 

 and Nansen Harbour join has been the most productive exposure for fossils in the 

 island. The fossils are described by Professor Gregory. 



Cumberland Bay. 



The rocks of the middle division, the rusty-brown type, are well developed. 

 They occupy both sides of the bay on the outer coast, and running up King Edward's 

 Cove form the lofty escarpment at the head of it. A fringe of the lower division 

 is seen coming in under the middle division at Sappho Point, and runs round to the 

 neighbourhood of the meteorological station. 



Mount Paget itself is formed of rocks of the middle division, an escarpment of 

 which, at its crest, can on a clear day be distinguished by its colour. The apparently 

 continuous section of middle and lower division rocks, rising out of Moraine Fiord to 

 the big wall-like escarpment on the shoulders of Mount Paget, we have already 

 noted, and it represents a thickness of 4215 feet. Of this thickness we have given 

 3000 feet as the part occupied by rocks of the middle division, the lower division 

 making up the remaining thickness. 



As Mount Paget is 8383 feet above sea-level, the rocks of the Middle Series, if 

 they were continuous, from Moraine Fiord to the top of it would be as follows : — 

 8383 — 4215=4168 feet thicker than we have estimated them, thus giving a total 

 thickness of 7168 feet. And as we know that rocks of the upper division occur 



